Describe the overall approach.
Confirm the diagnosis with imaging studies in patients with features suggestive of bronchiectasis.
Poor control or frequent exacerbations in patients with chronic pulmonary disease (e.g., COPD, asthma)
Chronic cough or recurrent pulmonary infections in patients with immunosuppression or conditions associated with bronchiectasis
Productive cough lasting > 8 weeks in otherwise healthy patients
Identify the underlying etiology.
Routine laboratory studies, sputum culture and smear, and pulmonary function tests
Clinical suspicion for a specific etiology: Obtain additional studies based on individual evaluation.
In patients with suspected bronchiectasis, diagnosis is confirmed using imaging studies, preferably a HRCT scan. Additional diagnostic studies are useful to identify the underlying cause and possibly provide specific treatment.
List imaging modalities and their respective findings.
X-ray chest: best initial test (may not show mild disease)
High-resolution computed tomography (HRCT) chest: confirmatory test
Cylindrical or tubular (most common) : parallel tram track sign and signet ring sign
Saccular or cystic (most severe form)
Thickened bronchial walls, mucus plugging, honeycombing (suggests late-stage bronchiectasis)
Describe the initial workup of identification of the underlying etiology.
Studies to determine the underlying etiology of bronchiectasis are usually requested by a specialist. In many cases, it is not possible to reach a specific diagnosis and the disease may be classified as idiopathic.
Perform at the time of diagnosis to obtain baseline references. Sputum culture and smear, as well as spirometry, are also used for monitoring.
Describe lab studies.
CBC: Findings are variable and depend on the underlying etiology.
Variable leukocyte levels
Consider ABG (e.g., in patients with ↓ SaO2 on room air): may show hypercapnia
Quantitative measurement of serum immunoglobulins and electrophoresis (IgA, IgG, IgM, and IgG subclasses): to exclude immunodeficiencies 
Aspergillus fumigatus IgG and IgE: to exclude ABPA
Describe sputum culture and smear.
culture induced sputum or bronchoalveolar lavage for all of the following pathogens to detect infection or colonization
Bacterial cultures: e.g., H. influenzae or P. aeruginosa
Fungal cultures: Candida spp. or Aspergillus spp.
Mycobacterial culture (with AFB smear microscopy): tuberculosis or nontuberculous mycobacteria
not needed to establish a diagnosis but useful to monitor disease progression 
Mixed obstructive/restrictive pattern
Restrictive pattern (i.e., ↓ FEV1 and FVC with normal or ↑ FEV1/FVC ratio)
Obstructive pattern (i.e., ↓ FEV1/FVC ratio)
List additional diagnostics.
These studies may be considered depending on clinical suspicion if the initial workup was not diagnostic.
Specific antibodies (e.g., rheumatoid factor, ANAs, anti-CCP antibodies, ANCAs): suspected connective tissue or autoimmune diseases
Sweat chloride test and/or genetic testing for CFTR mutations: suspected CF
HIV testing , serum α1-antitrypsin levels , nasal nitric oxide testing for primary ciliary dyskinesia
Indicated to visualize tumors, foreign bodies, or other lesions (most useful in patients with localized disease)
May also be used in combination with bronchoalveolar lavage (BAL) to obtain specimens for staining and culture
Upper GI studies (e.g., upper endoscopy, barium swallow, esophageal manometry): consider for suspected gastroesophageal reflux disease or recurrent pulmonary aspiration
Colonoscopy with biopsies: if associated inflammatory bowel disease is suspected (e.g., GI bleeding)
If the initial workup does not identify the underlying cause, perform further studies guided by the patient's clinical features and consider referral to a specialist.